The present invention relates to a small light-weight electric motor driven fluid pump of the type having an integrated motor and pump construction resulting in a simplified design and a minimum of static and/or dynamic seals.
Integrated electric motor-fluid pump assemblies have hereto been available but have generally exhibited an undesired complexity with a number of housing parts, protruding rotor shafts, and both static and dynamic sealing requirements.
It is the general object of the present invention to provide a small light-weight electric motor driven fluid pump assembly having a molded thermoplastic housing of no more than two mating parts which form a fluid impervious rotor chamber and which journal a stationary shaft carrying a magnetic rotor and a fluid impeller driven thereby, said housing requiring neither static nor dynamic seals and exhibiting a highly efficient integrated motor-pump design.
In fulfillment of the foregoing object and in accordance with the present invention, a light-weight electric motor driven fluid pump assembly is provided with a molded thermoplastic housing of no more than two parts which form a fluid impervious rotor chamber when assembled. A shaft is journalled within the housing at opposite ends respectively by said two housing parts and carries a rotor assembly comprising a magnetic rotor forming a first part of an electric motor and a fluid impeller driven thereby. The housing parts also define fluid and inlet discharge ports in communication with the rotor chamber adjacent the impeller and one of the housing parts which defines a portion of the rotor chamber has a relatively thin walled tubular ID) configuration with a cylindrical exterior surface in coaxial relationship with the magnetic rotor in the rotor chamber. An annular stator forming a second motor part is disposed on or about said exterior surface for magnetic co-operation with the rotor. Thus, the motor and pump are effectively integrated and there is no penetration of the housing other than the magnetic cooperation between the rotor mounted within the housing and the stator mounted externally thereof.
The two parts of the housing are joined in assembled relationship at mating surfaces and may be provided with a single continuous static seal between said surfaces, this of course constituting the most reliable of sealing arrangements. Preferably, however, there is no seal whatsoever between the two housing parts and, instead, the parts are joined in assembled relationship by a continuous weld, thus dispensing with the need for even a simple static seal. In order to facilitate effective fluid tight welding, one of the housing parts may be provided with a small continuous raised bead on its mating surface and the other of the parts may have a small continuous groove which receives and complements the bead. Finally, various welding techniques may be employed but in the presently preferred construction the two housing parts are secured in assembled relationship employing a sonic welding technique.